Having dispatched Karen Khachanov in straight sets 6-3, 6-4, 6-4, Murray used his courtside post-match interview to talk about the terror attacks at Manchester Arena and London Bridge that left 29 people dead and many more injured.
Nishikori settled again in the third set to force a tie-break, but the Japanese eighth seed imploded when it mattered - losing all seven points with a flurry of unforced errors.
"Obviously for a couple of points after that I was sacked up, because I was frustrated at that moment", Murray said in his news conference after his 2-6, 6-1, 7-6 (0), 6-1 win over eighth-seeded Nishikori.
Wawrinka, who was beaten by Murray at the same stage 12 months ago, has not dropped a set in his first five matches and has lost just 54 games, which equals his tally from 2015, when he won the title.
"Andy's much tougher to beat in best of five, he's worked so hard on his conditioning. I have never seen that", the three-time Grand Slam champion Murray said.
"The fourth, I think it was ideal tennis I played". The 32-year-old Swiss took just 100 minutes to dispose of the 2014 US Open champion to reach the semi-final for a third time in a row.
Rangers launch Europa League campaign against Progres Niederkorn of Luxembourg
Teams have to pass through three qualifying rounds and a play-off before making it to the group stage of the Europa League. They will host the first leg at Pittodrie on July 13 with the return the following week.
"It was ideal today, I'm very satisfied", said Wawrinka who will be playing in his third successive Roland Garros semi-final.
"Personally I think it was put down to the conditions. So I'm sure it's going be tough one, but I will try to enjoy it and try to win the match". I didn't do anything special, but that was a critical period of the match, because he started way better than me.
Murray said: "Obviously for a couple of points after that I was sacked up, because I was frustrated at that moment".
Nishikori hit back by winning the first game of the fourth against serve, but it was one-way traffic thereafter as an increasingly assured Murray cruised to victory.
Murray received an award for finishing 2016 as world number one, with brother Jamie sharing the men's doubles trophy with Brazilian partner Bruno Soares.
'Hopefully I can take advantage of that and find solutions to beat him'. I don't think he was as far away as people were saying.
The defending champion from Serbia lost to sixth-seeded Dominic Thiem 7-6 (5), 6-3, 6-0 in the quarterfinals.
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